1. Field of the Invention
The invention relates to a system and method for in-situ generation of fluorine radicals and/or fluorine-containing interhalogen compounds for use in semiconductor manufacturing processes, such as removal of solid residues or particles from semiconductor equipment.
2. Description of the Related Art
Semiconductor processing generally involves decomposition of relatively volatile precursors containing silicon (Si), tungsten (W), titanium (Ti), or tantalum (Ta) to form complex metal oxides or silicates. Such volatile precursors are notorious for forming solid residues inside the semiconductor processing chamber or on other internal components of the chamber, such as wafer carders, wafer transport mechanisms, and wafer platens.
As such, solid residues accumulate on the internal surfaces of the processing chamber, and solids occasionally flake off from the solid residue deposits to yield free particles floating inside the processing chamber. These free particles, when landing on semiconductor wafers, result in wafer contamination.
It therefore is desirable to remove accumulated solid residues from the interior wall surfaces and other internal parts of the processing chamber, without attacking the structural components of the processing chamber.
Convention methods used for cleaning semiconductor processing chambers and reactors include wet scrubbing and plasma-enhanced cleaning.
Wet scrubbing methods require disassembling each component part of the processing equipment, scrubbing each part with harsh chemical reagent(s) such as HF, H2SO4, H3PO4, and HNO3, rinsing the component parts with large volumes of deionized water, and reassembling those component parts.
Such approach has many inherent problems, including: the labor and time required for disassembling, cleaning, and reassembly; the high Mean-Time Off Line (MTOL) as a concomitant of the duration of the cleaning operation; the high volume of hazardous chemicals used; the risk of residual contamination; the incidence of excessive surface wear during the cleaning process; and the potential health issues related to worker exposure to hazardous chemicals.
Another conventional method for cleaning semiconductor processing chambers involves use of plasmas formed by applying radio frequency (RF) energy to perfluorinated precursors, such as CF4, NF3, C2F6, C2F8, and SF6. The plasmas thus formed will react with the accumulated solid residues inside the semiconductor processing chamber.
Perfluorinated (PFC) gases, however, are among the six strongest greenhouse gases targeted by the Kyoto Climate Protection Protocol of 1997. They generally have global warming potentials (GWPs) three (3) and four (4) orders of magnitude higher than CO2. Further, they are extremely stable molecules, tending to stay unchanged in the atmosphere for thousands of years. Moreover, most chamber cleaning systems utilizing plasma-enhanced cleaning techniques have low gas decomposition rates, resulting in high levels of PFC gases being released into the atmosphere.
Plasmaless or dry cleaning processes using chlorine trifluoride (CIF3) and other fluorine radicals and/or fluorine-containing interhalogens have recently proved to be effective in removing solid residues from semiconductor processing chamber. ClF3 and other fluorine radicals and/or fluorine-containing interhalogens react with such solid residues to form volatile reaction products, which can be readily removed from the processing chamber by vacuum or other devices. See Y. Saito et al., “Plasmaless Cleaning Process of Silicon Surface Using Chlorine Trifluoride”, Applied Physics Letters, vol. 56(8), pp. 1119-1121 (1990); also see D. E. Ibbotson et al., “Plasmaless Dry Etching of Silicon with Fluorine-Containing Compounds”, Journal of Applied Physics, vol. 56(10), pp. 2939-2942 (1984); also see Ashley U.S. Pat. No. 5,565,038 entitled “Interhalogen Cleaning of Process Equipment,” issued Oct. 15, 1996.
The use of fluorine radicals or fluorine-containing interhalogens for cleaning of semiconductor processing equipment, however, faces practical problems of implementation and commercial viability.
For example, the supply of fluorine radicals or fluorine-containing interhalogens, including ClF3, are highly corrosive, and issues such as compatibility of storage and dispensing vessels, and associated process piping and componentry, require substantial attention and costly solutions.
Further, interhalogen compounds are extremely irritating to human respiratory tracts. The threshold level of human tolerance of ClF3 vapor is as low as 100 ppb, and an LC 50, 1 hour of 300 ppm. Inadvertent leakage of such highly toxic fluid is therefore highly hazardous to human health. Further, most interhalogen compounds are liquids at room temperature and are transported in the liquid phase, and the inherent high density of liquids over gases accentuates many of the risks associated with transporting such compounds.
Thus, it would be a significant advance in the art to provide a system and method that generates fluorine radicals and/or fluorine-containing interhalogens with minimized risk of exposure to these compounds and that overcomes problems otherwise associated with transporting and storing highly reactive fluorine radicals and fluorine-containing interhalogens.